<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=gb2312" />
<title>??</title>
  <style>
    .layer1{background:blue;width:100%;height:200px;paddding:12px;}
	.layer1-1{background:black;width:30%;height:200px;paddding:12px;float:left;}
	.layer1-2{background:orange;width:40%;height:200px;paddding:12px;float:left;}
	.layer1-3{background:#AAAAFF;width:30%;height:200px;paddding:12px;float:left;}
	.layer1-4{clear:both}
    .layer2{background:yellow;width:100%;height:200px;paddding:12px;}
    .layer3{background:blue;width:100%;height:200px;paddding:12px;}
  </style>
</head>

<body>
    <div class="layer1"> 
	    <div class="layer1-1"></div>
		<div class="layer1-2"></div>
		<div class="layer1-3"></div>
		<div class="layer1-4"></div>
	</div>
    <div class="layer2"></div>
    <div class="layer3"></div>

</body>
</html>